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<h1>Value Viewer</h1>
<h2><code>loop.debug.Viewer</code></h2><br>
<p>Class of objects that generate human-readable textual representation of Lua values.
This class is typically used to print out value of variables, data structures or objects in a Lua application using a syntax similar to the Lua language.
It is useful for implementation of command line debug mechanisms.
This class can also be used as a simple serialization mechanism for a restricted set of Lua values.</p>

<p>Basically, each object provides an operation to print values and holds some information that defines how values should be displayed like the output used.</p>

<h2>Behavior</h2>

<h3>Fields</h3>

<dl>
	
	<dt><code><b>indentation</b></code></dt>
	<dd>
		String used to add an indentation level when writing nested tables.
To write tables without indentation or in a single line use the empty string. The default value of this field is a string with two blank spaces <i>i.e.</i> <code>'  '</code>.
	</dd>
	
	<dt><code><b>labels</b></code></dt>
	<dd>
		Table mapping values to their labels that are the strings that represent each value.
		The default value of this field is a table with all packages loaded at the moment this class is first required properly labeled.
	</dd>
	
	<dt><code><b>linebreak</b></code></dt>
	<dd>
		String used to add line breaks when writing tables.
		To write tables in a single line use a string with a space.
		The default value of this field is the string <code>'\n'</code>. 
	</dd>
	
	<dt><code><b>maxdepth</b></code></dt>
	<dd>
		Maximum number of levels of nested tables that should be visualized.
		When this value is negative all levels of nested tables are visualized.
		The default value of this field is -1.
	</dd>
	
	<dt><code><b>output</b></code></dt>
	<dd>
		Object used to write visualization of values.
		The object must provide the operation <code>write</code> that receives strings to be written.
		The default value of this field is the standard output file.
	</dd>
	
	<dt><code><b>prefix</b></code></dt>
	<dd>
		String written at the start of each new line of the visualization.
		The default value of this field is an empty string.
	</dd>
	
</dl>

<h3>Methods</h3>

<dl>
	
	<dt><code><b>label</b>(value)</code></dt>
	<dd>
		Method used to generate a label for a given value not already labeled in field <code>labels</code>.
		By default this method generates labels using the <code>tostring</code> method of Lua base library.
		If the value defines the <code>__tostring</code> meta-method then the original string representation is shown between parenthesis.
		This method may be redefined for each object in order to define other labeling policy.
	</dd>
	
	<dt><code><b>package</b>(name, pack)</code></dt>
	<dd>
		Method that adds labels for the package named <code>name</code> and defined by table <code>pack</code> as well as all its functions or <i>userdata</i> fields.
	</dd>
	
	<dt><code><b>print</b>(...)</code></dt>
	<dd>
		Method that writes the textual representation of all arguments to field <code>output</code>.
		However, string values are written directly without any transformation.
	</dd>
	
	<dt><code><b>tostring</b>(...)</code></dt>
	<dd>
		Method that returns a string with the textual representation of all the values passed as argument.
		The representations of each argument are separated by commas in the final representation.
	</dd>
	
	<dt><code><b>write</b>(...)</code></dt>
	<dd>
		Method that writes the textual representation of all arguments to field <code>output</code>.
		The representations of each argument are separated by commas in the final representation.
	</dd>
	
	<dt><code><b>writeto</b>(output, ...)</code></dt>
	<dd>
		Method that writes to object <code>output</code> the textual representation of all other arguments.
		The object <code>output</code> must provide the operation <code>write</code> that receives strings to be written.
		The representations of each argument are separated by commas in the final representation.
	</dd>
	
</dl>

<h2>Remarks</h2>

<ul>
	<li>This class can be used as an instance of itself, therefore all methods can be executed over the class itself.</li>
	<li>May be used to serialize into Lua code any value of type <code>nil</code>, <code>boolean</code>, <code>number</code>, <code>string</code> and <code>table</code>.
	However, serialized tables may not contain circular reference, other values that do not match this description, or string keys that match the name of a Lua keyword.
	To serialize values of other types, you should label them with a chunk of Lua code that is able to restore the value.</li>
</ul>

<h2>Examples</h2>

<h3><a name="GlobalState">Show part of the global state of Lua</a></h3>

<pre>
local Viewer = require "loop.debug.Viewer"

viewer = Viewer{
  maxdepth = 3,
  indentation = "|  "
}

viewer:write(_G)
</pre>

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<p><small><strong>Copyright (C) 2004-2008 Tecgraf, PUC-Rio</strong></small></p>
<small>This project is currently being maintained by <a href="http://www.tecgraf.puc-rio.br">Tecgraf</a> at <a href="http://www.puc-rio.br">PUC-Rio</a>.</small>
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